Electric-discharge machining which is conventionally referred to as EDM has been performed for many years by generating a voltage between an electrode and a workpiece through a dielectric fluid such that a spark momentarily generated removes a portion of the workpiece surface to perform machining. This general type of machining has more recently evolved into electric-discharge texturing wherein the surface of a workpiece is textured. For example, rolls used in steel mills to roll steel that is to be painted cannot be too smooth or the paint adhesion will not be good. Texturing of the rolls provides the rolled steel with a textured surface to which paint adheres better. This texturing is performed by electric-discharge texturing apparatus wherein a bank of electrodes are moved adjacent the roll surface as the roll is rotated. Electrode positioners ensure that each electrode is properly spaced with respect to the workpiece surface so as to be close enough to generate momentary sparks through dielectric fluid but not too close so as to generate a continuous current flow without any sparks to perform the texturing operation.
Electric-discharge texturing apparatus conventionally has its electrode positioners mounted in a bank of axial rows extending along the central axis of roll rotation and in generally circumferential columns with each electrode positioner moving its associated electrode along a feed axis toward and away from the roll. While it would be desirable for the feed axes of all of the rows to extend radially, this is not possible since the rolls to be textured can have different diameters.